I put Cardboard in front ofmy radiator, and now it runs cooler! Why?

[BlackFox5.0]

I put cardboard in front of the radiator so I would have more heat, (along with a new 195* T-stat) and my car won't go above 180 on my autometer gauge. Before it used to go up to around 185*. I don't understand how this can be possible, but it's happening. I put a piece that covers about 80% of the radiator. I also have an electric fan, which is never on.

 

[93 LX]

Well one explaination could be that the cardboard is causing a more directional air flow towards the botton of the radiator. This is causing that coolent to be cooled at a higher rate then before. I am sure at the high heat of summer this would cause over heating. Its similar to big riggs on the hyways closing the grill openings to keep the engine closer to operating temps.

-a